Electric attachment plug



Nov. 8, 1955 R. o. COLLINS ELECTRIC ATTACHMENT PLUG Filed Oct. 29, 1953 mrw 4 d WD mh .4 n

nited States Patent ELECTRIC ATTACHMENT PLUG Ralph D. Collins, Beverly Hills, Calif., assignor to Koiled Kords Incorporated, New Haven, Conn., a corporation of Illinois Application October 29, 1953, Serial No. 389,075

7 Claims. (Cl. 339-61) This invention relates to electric attachment plugs, and it relates more particularly to an improved plug connection having means for facilitating attachment to an electrical socket of a plug having its contact blades or prongs normally considerably out of registry with the openings of the electrical socket to which it is to be attached.

Numerous forms of attachment plugs have been proposed heretofore for preventing the plugs from being accidentally disconnected from their sockets. In many of these prior constructions, the contact blades are yieldably mounted in the body of the plug so that they may be moved relative to each other either before or while the blades are being inserted into the electrical socket. For instance, it has been suggested to set the longitudinal axes of the blades at a slight angle to one another, or to space the blades from each other a distance slightly greater or less than the distance between the openings of the socket, so that in either case when the plug is attached to the socket it tends to grip the socket terminals and to resist accidental removal of the plug from the socket. However, in these prior attempts to obtain a firmer connection between the plug and the socket, the extent to which the blade may be out of registry with the openings of the socket is necessarily limited because, if they are too far out of line with the socket openings, it becomes extremely difficult if not impossible to insert the blades into the openings.

The present invention, therefore, provides an improved attachment plug construction, which permits the blades to be mounted considerably out of registry, in any of a number of different ways, with the socket openings, thereby making possible a firmer connection between the plug and the socket than has been practical to achieve heretofore and, still more important, permitting the blades to be easily moved into registry with the openings of an electrical socket as the connection is made.

In general, the above and other objects of the invention are carried out by providinga plug having a plug body, in which are yieldably mounted two or more contact blades which extend outwardly therefrom for insertion into the openings of an electrical outlet, the blades being normally positioned so that they must be moved or bent relative to each other in order that they may be inserted into the socket openings, and at least one of the blades being longer than the other or others to provide means for obtaining a purchase by which said blades can be easily moved relative to the plug body so that all the blades may be made to register with the corresponding openings in the socket for attachment of the plug thereto.

In a particularly desirable embodiment of the invention, the blades are fiat metal strips, which are mounted in the plug body with their flat sides at an angle with respect to each other, one of the blades being somewhat longer than the other. Thus, in order. to connect the plug to a conventional socket member having a pair of parallel rectangularly shaped openings or slots, the longer blade of the plug is inserted in one of the openings first, and the plug body is then twisted about this blade until the other blade comes into registry with the second socket opening, whereupon both blades may be slid into their corresponding openings in order to complete the connection. If the blades are mounted in a plug body made of resilient material such as rubber or plastic, as is most desirable, distortion of the plug body by twisting it in the aforesaid manner causes the blades to grip the terminal contacts within the electrical socket and to resist removal of the plug therefrom.

Other objects and advantages of the invention will become more apparent from the following detailed description of certain specific embodiments of the invention shown in the accompanying drawings, in which:

Fig. 1 is a side elevation of one form of electrical plug embodying the invention; Fig. 2 is a plan view of the plug of Fig. 1;

Fig. 3 is another view of the plug shown in Figs. 1

her or plastic type in which a pair of metallic contact blades 12 and 14 are embedded in the plug body during the molding operation thereof. Plugs of this type may be manufactured, for instance, in a manner similar to that disclosed in the patent to Judisch 2,500,546 issued March 14, 1950. In the particular embodiment of the invention shown in Figs. 1-4, the blades are of fiat brass strip-metal stock, the embedded ends of which are suitably connected to the bared ends of separate insulated conductors or wires of an electric cord 16, which is also embedded in the plug'body during the molding operation. Blades 12 and 14 are connected to the wires of cord 16 by clamping the ends of the blades over the bare wires, by soldering or by some other accepted manner of making a good electrical connection.

The plug body 10 may be of any desired shape, but as shown in the accompanying drawings it is more or less rectangular in cross section and is provided with finger grips 17, which aid in removing the plug from an electrical outlet. Blade 12 is embedded in the plug body 10 with its flat side perpendicular to the longer side of the plug, as best shown in Fig. 2, this being the usual position for the blades or prongs in order that they may be inserted into conventional socket fixtures or electrical outlets. Blade 14, on the other hand, instead of being located in the usual manner parallel to blade 12 for insertion into the socket, is mounted in the plug body at an angle with respect to blade 12 and must be twisted in its mounting to bring it into parallel therewith before the blades can be inserted into the socket. Thus, as is clearly shown in Figs. 1 and 2, blade 14 has its flat side set at an angle to that of blade 12.

Moreover, as best seen in Fig. 3, blade 14 is somewhat longer than blade 12 so that it can be partially inserted into one of the pair of slots or openings 18, 20 in a conventional electrical socket fixture 22, while blade 12 is still completely free of the socket. It now becomes readily apparent that in order to insert the blades of the attachment plug into the socket 22, the tip of blade 14 is first inserted into one of the socket openings 20, for instance, and the plug body 10 is then twisted about this blade Fig. 4) to bring blade 12 into registry with the socket opening 18, whereupon both blades may be pushed into engagement with the terminal contacts within socket 22.

Since the openings in the socket 22 are of rectangular shape and are only slightly larger than the flat blades of the plug, the blade 14 will of course not turn in the socket when the plug body 10 is twisted. Therefore, since the tip of the longer prong is held firmly in the socket against twisting, the plug body 19, being of a resilient material such as rubber or plastic, can be readily distorted despite considerable resistance thereto, in order that the prongs can be brought into proper registry, with the openings in the socket. After the blades are started into the socket openings by obtaining a good purchase in one of the openings with the longer blade and twisting the plug so that the other blade may be inserted into the second opening of the socket, the prongs of the plug are pressed their full extent into the socket and are forced laterally against the contact terminals of the socket by the tendency of the resilient plug body to return to its normal condition. This increases the friction between the blades of the plug and the socket, thereby providing a considerable degree of resistance to removal of the plug from the socket fixture. The more the blades are initally placed out of registry with the socket openings, the more resistance to removal of the plug is obtained. Due to the fact that the prongs of plugs according to the present invention are of different lengths and, therefore, are capable of being readily moved with respect to each other by obtaining a purchase in one of the socket openings with the longer blade or prong, it becomes entirely practical to obtain a much greater amount of friction between the plug blades and the socket than has been possible. heretofore without providing a special type of plug body or blade mounting for changing the relative positions of the blades with respect to each other.

It is of course apparent that either or both of the blades of the plug could be set at an angle to the other and, moreover, that the longer blade need not necessarily be the one which is initially positioned out of alignment with respect to the plug body. Thus, blade 12, rather than blade 14 as hereinabove disclosed, could be the longer blade, in which case it of course would be the first to be inserted in the socket, and the plug would then have to be twisted about blade 12 instead of as hereinbefore described.

It should be noted here that in the plug shown in Figs. 14, the longitudinal axes of the blades 12 and 14, are parallel. while the flat sides of the blades are at an angle, so. that the blades are normally positioned out of registry with the openings in a socket for which the plug is intended. However, in another embodiment of the invention shown in Figs. and 6, the fiat sides of both prongs of the plug are parallel, while the longitudinal axis'of the blade 14a is normally set at an angle to the longitudinal axis of blade 12. As best seen in Fig. 5, blade 12 extends'perpendicularly from the end of the plug body as in the previously described embodiment of the invention, while blade 14a diverges from blade 12. Moreover, blade 14a is longer than blade 12 so that, when the tip of this blade is inserted into an opening of an electrical socket, it may be readily moved into parallel with blade 12, thereby permitting insertion of both blades into the socket.

Since blade 14a is molded into the plug body with its, longitudinal axis initially out of parallel with that of blade 12, the blades will, upon being brought into parallel by connecting the plug to a socket, exert pressure on the internal parts of the socket due to the distortion of the plug body by the change in position of the blades relative to each other. Consequently, when the prongs of the plug are completely inserted in the socket, the resistance to removal of the plug from the socket is considerably increased with respect to the conventional type of electrical connection.

Although blade 14a is shown extending away from blade 12, it is readily apparent that it may extend toward blade 12 or that both blades may be set at angles to the longitudinal axis of the plug so that they either converge or diverge toward or away from each other as they extend from the plug. In this particular form of the invention, since the plug does not have to be twisted about the blades, the blades need not be flat or rectangularly shaped as in the previously described embodiment of the invention, and they may therefore be of circular cross section, for instance. Furthermore, the blades of the plug in any of the illustrations hereinabove given could be spaced apart a distance either greater or less than the distance between the openings in the electrical outlet to which the plug is intended to be connected, so that the blades would have to be moved or sprung bodily laterally, in order to fit completely into the socket.

It is also clearly within the scope of this invention, where the blades are flat or noncircular in cross section, both to set at least one of the blades in a twisted position with respect to the other blade, as in the plug shown in Figs. 1 and 2, and to mount the blades with their longitudinal axes out of parallel, as shown in Figs. 3 and 4. In this case, the plug would have to be twisted as well as moved laterally after the longer blade is inserted into one of the openings of a socket, in order to align the other blade with the second opening before the connection of the plug with the socket can be completed. In any event, as a fundamental feature underlying the pres ent invention, one of the blades must be longer than the other in order to obtain the necessary point of purchase of at least one of the blades in an opening of the socket.

The foregoing specific disclosure of certain embodiments of the invention shown in the drawings has been limited to attachment plugs having only two contact blades. The invention is of course equally applicable and is extremely useful in electrical connections having three or. more contact members, since at least one of the blades of a plug having more than two prongs can be made longer than the remainder for the purpose hereinabove described.

It has been found that if the blades differ in length by an eighth of an inch in conventional lighting and appliance connectors, a plug embodying the present invention may be readily connected to a standard electrical outlet. However, any difierence in the length of the prongs would be satisfactory so longas at least one of the blades is willciently longer than. the others to obtain a good purchase in one of the socket openings so that the blades can be easily moved relative to each other.

What is claimed is:

l. in an attachment plug, a plug body and a plurality of spaced contact blades yieldably mounted in said plug body and extending outwardly therefrom for insertion into openings in an electrical socket, said blades being normally out of registry with the openings in the electrical socket and at least one of said blades being longer than the remainder in order to provide for preliminary insertion into its socket opening to form a point of purchase against which, through pressure applied to the plug body, the blade mounting can be made to yield so as to bring all of the blades into registry with their socket openings.

2. In an attachment plug, a plug body and a pair of spaced contact blades yieldably mounted in said plug body and extending outwardly therefrom for insertion into openings in an electrical socket, said blades being normally out of registry with the openings in the electrical socket and one of said blades being longer than the other to provide for preliminary insertion into its socket opening to form a point of purchase against which the plug body can be deformed to bring the other blade into registry with its socket opening.

3. An attachment plug as defined in claim 2 wherein said blades are elongated flat metal strips, the flat faces of said blades being normally at an angle with respect to each other.

4. An attachment plug as defined in claim 3 wherein the longitudinal axes of said blades are parallel.

5. An attachment plug as defined in claim 2 wherein the longitudinal axes of the blades are at an angle to each other.

6. An attachment plug as defined in claim 2 wherein tween said socket openings, the flat faces of said blades being normally at an angle with respect to each other and one of said blades being longer than the other to provide for preliminary insertion into its socket opening to form a point of purchase against which the plug body can be deformed by twisting until the blades are parallel and the shorter blade is in alignment with its socket opening for insertion therein.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,827 Herman July 22, 1941 2,292,554 Weeber Aug. 11, 1942 2,408,583 Sions Oct. 11,1946 2,478,570 Crehan Aug. 9, 1949 

